Metallic lids of the type mentioned above are well known. They are formed in a single piece of metal sheet and comprise a generally disk shaped bottom wall, whose peripheral edge incorporates a side wall projecting upwardly, so as to be removably press fitted and axially retained inside a seat defined in an upper opening of a can. Said seat can be defined by a depending tubular projection which is superiorly incorporated to a median opening of the upper wall of a can with a circular or polygonal section.
Metallic lids of the type mentioned above are disclosed and illustrated in U.S. Pat. No. 2,074,231, U.S. Pat. No. 3,347,408, BR-MU8002622-2, BR-MU8002618-4, BR-PI9408643-5 and BR-MU7601221-2, the last two pertaining to the same applicant of the present patent application.
In these prior art constructions, the lid structure comprises only the bottom wall and a peripheral side wall, and the axial retention of the lid in the seat defined in the upper opening of the can is usually achieved through engaging means provided in at least one of the parts defined by the parts of lid side wall and seat in the upper opening, in order to operate with the other part.
In the construction above, even when the bottom wall of the lid presents a drawn or raised median portion, as taught in the solution disclosed in patents BR-MU7601221-2 and U.S. Pat. No. 3,347,408, the lid structure requires certain cares to be taken when closing forces are applied, otherwise the lid can be irremediable damaged, avoiding a tight and secure closure of the can.
The structural deficiency mentioned above is due to the fact that said lid construction lacks the usual peripheral strength guaranteed in the metallic lids provided with a peripheral annular recess, generally with an inverted substantially trapezoidal cross section, to be frictionally seated in the interior of a recess with a complementary cross section an which defines a seat incorporated to the annular upper wall of a can body, such as in the construction known for decades and which is disclosed and illustrated in U.S. Pat. No. 795,126, filed in 1904.
In this very well known construction, the structure of the lid allows the latter to be pressed when placed on the upper annular wall of the can, without the risk of producing plastic deformations in the profile of the lid, preventing the latter from being tightly retained in its seat in the can.
The construction of the peripheral recess, jointly with its region to which the raised median portion of the lid is joined, imparts a high structural strength to said lid, allowing the users to close the can by seating the lid and applying force in different locations in the lid, without the risk of the lid being deformed or losing its original shape.